std::atof

From Cppreference

C++ Standard Library
Language Utilities library Strings library Containers library Algorithms library Iterators library Numerics library Input/output library Localizations library Regular expressions library (C++0x feature) Atomic operations library (C++0x feature) Thread support library (C++0x feature)
Strings library
Narrow character strings Wide character strings Classes basic_string char_traits Functions getline stoi stol stoll stoul stoull (C++0x) (C++0x) (C++0x) (C++0x) (C++0x) stof stod stold (C++0x) (C++0x) (C++0x) to_string (C++0x) to_wstring (C++0x)
Narrow null-terminated strings
Functions Character manipulation isalnum isalpha islower isupper isdigit isxdigit iscntrl isgraph isspace isprint ispunct tolower toupper Conversions to numeric formats atof atoi strtol strtoul strtof String manipulation strcpy strncpy strcat strncat strxfrm String examination strlen strcmp strncmp strcoll strchr strrchr strspn strcspn strpbrk strstr strtok Memory manipulation memchr memcmp memset memcpy memmove Miscellaneous strerror

Defined in header <cstdlib>
​double atof( const char *str );​

Interprets an floating point value in a character string pointed to by str.

Function discards any whitespace characters until first non-whitespace character is found. Then it takes as many characters as possible to form a valid floating point representation and converts them to floating point value. The valid floating point value can be one of the following:

• decimal floating point expression. It consists of the following parts:

• (optional) plus or minus sign
• nonempty sequence of decimal digits optionally containing a decimal point character (defines significand)
• (optional) e or E followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent)

• binary floating point expression. It consists of the following parts:

• (optional) plus or minus sign
• 0x or 0X
• nonempty sequence of hexadecimal digits optionally containing a decimal point character (defines significand)
• (optional) p or P followed with optional minus or plus sign and nonempty sequence of hexadecimal digits (defines exponent)

• infinity expression. It consists of the following parts:

• (optional) plus or minus sign
• INF or INFINITY ignoring case

• not-a-number expression. It consists of the following parts:

• (optional) plus or minus sign
• NAN or NAN(char_sequence) ignoring case of the NAN part. char_sequence can only contain alphanumeric characters. The result is a quiet NaN floating point value.

Contents 1 Parameters 2 Return value 3 Example 4 See also

Parameters

str

-

pointer to the null-terminated character string to be interpreted

Return value

​double​ value corresponding to the contents of str on success. If the converted value falls out of range of corresponding return type, HUGE_VAL is returned. If no conversion can be performed, ​0.0​ is returned.

This section is incomplete Reason: fix links to limits

Example

This section is incomplete

See also

strtof strtod strtold	converts a character string to a floating point value (function)